Enhanced life barrel

ABSTRACT

A firearm having a stock and an enhanced life barrel attached to the stock. The enhanced life barrel has a tapered bore and either parabolic or 5R rifling. The barrel includes a chamber and a throat. Each of the tapered bore, the chamber, and the throat are lapped and polished to a finish of about 15Ra of better. The enhanced life barrel includes a ferritic nitrocarburizing finish of greater than about 0.0003 inches thick.

CROSS REFERENCE TO RELATED APPLICATION

Noon This application claims the benefit of U.S. Provisional Application No. 61/378,453, filed Aug. 31, 2010, entitled “ENHANCED LIFE BARREL”, the aforementioned application being hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a barrel and more particularly to a rifle barrel having an enhanced life.

BACKGROUND OF THE INVENTION

Many service firearms, such as the M4 rifle, employ ammunition that generate high bullet velocities and high temperatures than commercial ammunition. This ammunition also utilizes harder bullet jackets, which increases friction with the barrel. An example of such ammunition is the 5.56×45 mm NATO or “M855” cartridge.

One potential issue resulting from the combination of high pressure, high temperatures, and increased bullet friction is an increase in the wear of the barrel. As a result, the barrel life is reduced, which causes reduced muzzle velocity and an increase in repeatable group size.

As will be appreciated, it is generally desirable to increase barrel life of such firearms as much as practicable. More specifically, it is desirable to increase the barrel life of a rifle shooting M855 ammunition to at least 15,000 rounds.

SUMMARY OF THE INVENTION

Accordingly, it is a general object of the invention to provide a barrel having an enhanced life.

It is an additional object of the present invention to provide a barrel having an enhanced life through the use of a tapered parabolic rifled barrel.

It is an additional object of the present invention to provide a barrel having an enhanced life through the use of a tapered barrel having 5R rifling.

It is yet another object of the present invention to provide a barrel having an enhanced life through the use of a lapped and polished bore, groove, chamber and throat.

It is another object of the present invention to provide a barrel having an enhanced life through the use of a ferritic nitrocarburizing steel finish, also known as a QPQ or Melonite®, to a depth of over 0.0003″.

It is an additional object of the present invention to provide a barrel having an enhanced life through the use of a combination of a tapered parabolic or 5R rifled barrel, a lapped and polished bore, groove, chamber and throat, and a relatively “thick” ferritic nitrocarburizing finish.

These and other features, aspects and advantages of the present invention will be better understood in view of the following drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a barrel according to an embodiment of the present invention; and

FIG. 2 is a cross-sectional view of the barrel taken along line 2-2 of FIG. 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

As stated, many service firearms employ ammunition that generate high bullet energies and velocities, such as the M855 cartridge. A potential problem resulting from the combination of high pressure and temperature generated by these cartridges is an increase in the wear of the barrel, and as a result, a reduced barrel life. As will be appreciated, it is generally desirable to increase barrel life of such firearms as much as practicable and, in particular, to increase the barrel life of an M4 rifle shooting M855 ammunition to 15,000 rounds or greater.

An embodiment of the present invention increases barrel life through the use of a combination of barrel features, each of which contribute to enhanced barrel life. These features are discussed below.

An embodiment of the present invention employs a barrel 10 having a tapered bore 18 that includes either parabolic or 5R rifling 20. The bore may taper, for example, from an initial diameter D₁ at a breech end of the barrel, having a chamber 16, to a slightly reduced diameter D₂ at a muzzle end 14 of the barrel 10. Indeed, the muzzle end diameter may be 0.001 less than the breech end diameter.

The tapered barrel may include parabolic or 5R rifling. Parabolic rifling is known rifling that consists of “lobes” rather than grooves with distinct edges. 5R rifling uses five (5) lands and 5 grooves instead of the traditional six (6) lands and grooves. In addition, the sides of each land are cut at an angle θ. Angle θ may be about 65-degree angle as opposed to a 90-degree angle on standard rifling. Both of these rifling geometries generate less bullet fouling and allow the user to more easily clean the barrel. Less fouling and better cleaning of the bore of the remaining fouling enhance and promote better accuracy.

The above-described embodiment may also include a lapped and polished bore, groove, chamber, and throat. As will be appreciated, lapping results in smooth and flat barrel surfaces. In particular, the inventive embodiment contemplates lapping the aforementioned surfaces so that they have a Ra of 15 or better, i.e., the peaks and valleys on the barrel surfaces average no more than 15 microinches over a given distance.

In addition to the above, an embodiment of the present invention may include barrel surfaces having a ferritic nitrocarburizing (QPQ or Melonite®) finish. The finish reduces friction in the bore, lessens bore surface wear, and resists erosion from the powder gages to extend barrel life. In particular, the relatively thick finish is contemplated, and, in particular, a finish having a depth greater than 0.0003″.

An embodiment of the barrel may include tapered barrel having parabolic rifling, a bore lapped to a finish of 15 Ra or better and a ferritic nitrocarburizing finish to a depth greater than 0.0003″. In certain circumstances, this embodiment may omit either the lapping or ferritic nitrocarburizing finish without departing from the spirit and scope of invention.

In yet other embodiments, the barrel may include a tapered barrel having 5R rifling, a bore lapped to a finish of 15 Ra or better and a ferritic nitrocarburizing finish to a depth greater than 0.0003″.

It is to be understood that the above description is intended to be illustrative, and not restrictive. While each of the elements described is known to those skilled in the art the combination of these various elements results in a significant increase in barrel life. While the dimensions and types of materials described herein are intended to define the parameters of the invention, they are by no means limiting and are exemplary embodiments. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description.

This written description uses examples to disclose several embodiments of the invention, including the best mode, and also to enable any person skilled in the art to practice the embodiments of invention, including making and using any devices or systems and performing any incorporated methods.

As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property.

Since certain changes may be made in the above-described enhanced life barrel, without departing from the spirit and scope of the invention herein involved, it is intended that all of the subject matter of the above description shall be interpreted merely as examples illustrating the inventive concept herein and shall not be construed as limiting the invention. 

1. A firearm comprising: a stock; and an enhanced life barrel attached to the stock; the enhanced life barrel having a tapered bore and rifling extending along at least a portion of the tapered bore, the rifling being selected from the group consisting of parabolic and 5R.
 2. The firearm of claim 1, wherein the rifling includes five lands and five grooves, each of the five lands having sides formed at an angle of about 65° to a top of the land.
 3. The firearm of claim 1, wherein the tapered bore being lapped and polished.
 4. The firearm of claim 3, wherein the lapped and polished, tapered bore has a finish of about 15 Ra of better.
 5. The firearm of claim 1, wherein the enhanced life barrel includes a chamber and a throat, each of the chamber and the throat being lapped and polished.
 6. The firearm of claim 1, wherein the enhanced life barrel includes a ferritic nitrocarburizing finish about an inside and an outside of the enhanced life barrel.
 7. The firearm of claim 6, wherein the ferritic nitrocarburizing finish having a thickness greater than about 0.0003 inches.
 8. A enhanced life barrel comprising: a tapered bore therethrough, the tapered bore being lapped to a finish of about 15Ra or better; a parabolic rifling extending along at least a portion of the tapered bore; and a ferritic nitrocarburizing finish about an inside and an outside of the enhanced life barrel to a depth of greater than about 0.0003 inches.
 9. A enhanced life barrel comprising: a tapered bore therethrough, the tapered bore being lapped to a finish of about 15Ra or better; a 5R rifling extending along at least a portion of the tapered bore, the 5R rifling having five lands and five grooves; and a ferritic nitrocarburizing finish about an inside and an outside of the enhanced life barrel to a depth of greater than about 0.0003 inches. 